The present invention relates to electromagnetic coupling, and more particularly to inductive couplings for wirelessly providing power to a remote device.
There is an increasing demand for wireless power supply to remote devices, such as cell phones, digital music players, personal digital assistants and other similar electronic devices. As the use of handheld electronics continues to grow, so does the associated need for wireless power supply. Typical handheld electronics utilize a removable power supply cord that permits the device to be selectively coupled to a power source. Power supply cords are inconvenient and suffer from a variety of other problems. For example, a user is required to locate and attach the power supply cord each time that the device needs to be charged. Unless a user is willing to purchase multiple power supply cords or carry around a single power supply cord, the user must return to a single location to charge the device. As another example, power supply cords occupy a fair amount of space and are messy to store. Power cords and any associated power supply circuitry can present significant additional cost to the user. Although even a single power cord presents significant problems, the problems are compounded exponentially for those individuals or organizations that need to control power for a collection of remote electronic devices.
To address this issue, a variety of technologies have been developed to wirelessly supply power to remote devices. These technologies typically involve the use of electromagnetic coupling (or inductively coupling) that provides a wireless bridge between the power supply and the remote device. For example, U.S. Pat. No. 6,825,620 entitled, “Inductively Coupled Ballast Circuit”, U.S. Pat. No. 7,212,414, entitled “Adaptive Inductive Power Supply”, and U.S. patent application Ser. No. 10/689,148 entitled “Adaptive Inductive Power Supply with Communication” are directed to particularly efficient inductive coupling technology in which the power supply adjusts to the power supply needs of the remote device based on feedback from the remote device through the inductive coupling. These patents are incorporated herein by reference in their entirety.
Although inductive coupling technology has made significant progress over the last decade, there will always be a desire for greater efficiency, improved performance and smaller components.